Pilot-operated directional control valve, particularly for controlling an actuating cylinder of a turbo-machine

ABSTRACT

A directional control valve for controlling working cylinders, servomotors, or an actuating cylinder of a turbo-machine such as gas and steam turbines, the directional control valve includes a force-regulated magnet and a hydraulic unit. The hydraulic unit includes a pilot piston and a control housing in which the pilot piston is situated so it is displaceable in an axial direction of the directional control valve. The control housing has at least three hydraulic connections including a first pressure connection configured for connection to a hydraulic pressure supply, at least one consumer connection configured for connection to the working cylinder or the servomotor, and a tank connection configured for connection to a hydraulic tank. A flow cross-section between the hydraulic connections being variable by displacement of the pilot piston. The valve also having an actuating unit that includes a control piston, an actuating piston, a first elastic element, a second elastic element and a conductor. The control piston is displaceably located in the control housing or in a flange attached on the control housing. The control piston is displaceable using the force-regulated magnet, the control piston being configured to vary the flow cross-section between an actuating unit pressure connection, an actuating piston connection and an actuating tank connection by displacement. The actuating piston is non-positively and/or positively connected on the pilot piston such that the actuating piston is displaceable in the axial direction of the directional control valve. The actuation piston divides a piston room into a first piston room chamber and a second piston room chamber, the chambers being sealed from one another. The first piston room chamber is hydraulically connected to the actuating piston connection. The first elastic element acts against a hydraulic pressure force in the first piston room chamber. The actuating piston being connected by way of the first elastic element to the control piston or being supported thereon. The second elastic element acts against the hydraulic pressure force in the first piston room chamber. The actuating piston being connected by the second elastic element to the control housing or the flange or being supported thereon. The conductor is situated in a magnetic field of the force-regulated magnet. The force-regulated magnet being an electromagnet configured for electrical activation. The conductor is electrically connected to the electromagnet and a control unit for control of the electromagnet such that the magnetic force and the position of the control piston, the actuating piston, and the pilot piston are regulated by way of a Hall voltage generated in the conductor.

The present invention relates to a directional control valve forcontrolling working cylinders or servomotors, in particular forcontrolling an actuating cylinder of a turbo-machine, such as a gas orsteam turbine, a control piston (pilot piston) of the directionalcontrol valve being displaced using a force-regulated magnet and thusvarying the flow cross-section between hydraulic connections and/oralternately producing connections between various connection pairs.

The use of directional control valves for the control and/or positionregulation of working cylinders is known. For single-acting cylinders,for example, 3/3 directional control valves having spring return areused and 4/3 directional control valves having spring return are usedfor double-acting cylinders. These each have a control piston, which isactuated via an electromagnet. The electromagnet presses the controlpiston against a spring and thus connects a pressure connection P to aconsumer connection and/or one of two consumer connections A, B, inorder to conduct pressurized hydraulic medium via the particularconnection into a predetermined chamber of the consumer. For example, inthe case of double-acting working cylinders, the consumer connection Ais connected to a first cylinder chamber of the working cylinder, andthe consumer connection B is connected to a second cylinder chamber,which is separated by a cylinder piston from the first cylinder chamber.Depending on which of the cylinder chambers pressurized hydraulic mediumis to be introduced into from a hydraulic pressure supply via adirectional control valve, a piston rod attached to the piston of theworking cylinder is retracted or extended.

In such double-acting cylinders, the 4/3 directional control valve istypically implemented in such a manner that whenever the first consumerconnection A and thus the first cylinder chamber of the working cylinderis connected to the pressure connection P, the second consumerconnection B and thus the second cylinder chamber of the workingcylinder is connected to a tank connection T of the directional controlvalve or vice versa. The tank connection T is distinguished by acomparatively low hydraulic pressure, so that hydraulic medium slidesout of the cylinder chamber connected to the tank connection T and isguided to a hydraulic tank.

Depending on whether and how far the control piston of the directionalcontrol valve is displaced using the electromagnet against the pressureforce of the restoring spring, either the first consumer connection A isconnected to the pressure connection P or the second consumer connectionB is connected to the pressure connection P and the particular otherconsumer connection is connected to the tank connection T. Hydraulicmedium thus either flows to one or the other side of the piston of theworking cylinder and the retraction or extension of the piston and/or apiston rod of the working cylinder, which is attached to the piston, iscontrolled.

In order to position the piston with its rod at a position, a closedcontrol circuit is required. For this purpose, a position measuringdevice, also referred to as a position encoder, is provided on theworking cylinder, whose measuring signal is returned to controlelectronics integrated in the electromagnet of the directional controlvalve. These control electronics compare the measured value to thetarget value and calculate a new manipulated variable for the magnetfrom the difference. The force of the magnet then accordingly increasesor decreases and displaces the control piston in the required directionin order to correct the location of the piston of the working cylinder.The control piston of the directional control valve is non-positivelyconnected to the magnet armature of the electromagnet, i.e., the part ofthe magnet which is retracted or extended from the magnet by varying thecontrol voltage or the control current strength, and the adjustmentmovement of the control piston is performed directly by the magnetarmature, i.e., both components—magnet armature and controlpiston—always move jointly in the displacement direction of the controlpiston.

The flow cross-section between the consumer connection A, B and thepressure connection P and/or the tank connection T is determined by aring gap, which the control piston delimits with a control housing, inwhich it is situated so it is displaceable in the axial direction.Because the stroke of the electromagnet is limited, the flowcross-sections which a typical directional control valve can open andclose are limited. The diameter of the control piston also cannot beenlarged arbitrarily in order to thus expand the flow cross-sections,because its mass thus increases and it could no longer be exactlydynamically positioned in connection with a spring in the closed controlcircuit by the magnet. In particular, the occurring mass forces, naturalfrequencies, friction forces, and oscillations are to be viewed asproblematic.

To be able to use directional control valves for controlling actuatingcylinders of turbo-machines in spite of the described problems, having alarger control piston diameter for enlarging the flow cross-sections inthe directional control valves, on the one hand, there is thepossibility of implementing the electromagnets used as larger andstronger. However, this would also result in higher inductances andlarger armature masses, which would have disadvantageous effects on thedynamic response, the required installation space, and the costs of thedirectional control valve.

In another design, additional position measuring devices and/or positionencoders are provided, using which the position of the control piston ismeasured, and the measuring signal is returned to the controlelectronics of the electromagnet. An enlargement of the magnet is notnecessary in these embodiments. However, the sensitivity of the positionencoder with respect to temperature and oscillation influences isdisadvantageous. In particular in the case of the use of such adirectional control valve for controlling and/or regulating an actuatingcylinder of steam turbines or gas turbines, the high ambienttemperatures of the position encoder, which are caused by the medium ofgas or steam, which is to be varied with respect to its flow quantity,result in short maintenance intervals and possibly a comparatively earlybreakdown of the directional control valve.

The present invention is based on the object of disclosing a directionalcontrol valve which is improved with respect to the known embodiments.In particular, the directional control valve according to the inventionis to be able to position the piston rod of a comparatively largeworking cylinder (single-acting or double-acting) rapidly and exactlyand to control the accordingly required large flow quantities preciselyand reliably by the directional control valve. Finally, the directionalcontrol valve is to be producible cost-effectively and is to have a longlifetime.

The object according to the invention is achieved by a directionalcontrol valve having the features of claim 1. The dependent claimsdescribe particularly advantageous embodiments of the invention.

A directional control valve according to the invention for controllingworking cylinders, servomotors, or the like, in particular forcontrolling an actuating cylinder of a turbo-machine, such as a gas orsteam turbine, has, in addition to a force-regulated magnet, typicallyan electromagnet, a hydraulic unit, which comprises a control housing,in which a control piston—referred to as a pilot piston in the presentcase—is situated so it is displaceable in the axial direction of thedirectional control valve. The control housing has at least threehydraulic connections, for example, precisely three hydraulicconnections, in order to implement a 3/3 directional control valve, orfour hydraulic connections, in order to implement a 4/3 directionalcontrol valve, namely a pressure connection P, a consumer connection Aand/or B, and a tank connection T. The pressure connection P is intendedfor connection to a hydraulic pressure supply and the tank connection Tis intended for connection to a hydraulic tank. The consumerconnection(s) A, B is/are intended for connection to a consumer, theworking cylinder or the servomotor here.

The flow cross-section between the hydraulic connections A, B, P, T isvaried by displacing the pilot piston, as was described in theintroduction to the description. However, an additional actuating unitis provided according to the invention for the hydraulic unit, whichcomprises, on the one hand, the force-regulated magnet and an additionalcontrol piston, which is situated so it is displaceable in the controlhousing or in a flange attached to the control housing. The term flangerefers to any suitable structural form of an additional housing or areceptacle device, which can be implemented integrally with the controlhousing or can be attached thereto, typically non-positively andpositively. The control piston is associated with the force-regulatedmagnet in such a manner, in particular supported on a magnet armaturethereof or connected non-positively and/or positively thereto, that thecontrol piston is displaced by the force-regulated magnet as a functionof the activation of the magnet. The activation of the magnet, which isimplemented as an electromagnet, using a greater voltage or a greatercurrent strength will typically extend the magnet armature further, inparticular against the force of an elastic element, such as acompression spring, and thus press the control piston in a directionaway from the magnet. In the case of a lower control voltage or a lowercurrent strength, the magnet armature retracts correspondingly, inparticular due to the force of the elastic element or the compressionspring.

The additional actuating unit has an actuating unit pressure connectionp, an actuating unit tank connection t, and an actuating pistonconnection a. The actuating unit pressure connection p can particularlybe connected to a separate pressure supply, which is separated withrespect to the pressure connection P and/or the pressure supply of thecontrol housing, and is thus protected from pressure drops due topossible large volume flows through the hydraulic unit.

The actuating unit tank connection t can be connected to the hydraulictank which is associated with the hydraulic unit or to an additionalhydraulic tank.

The actuating unit also has an actuating piston according to theinvention, which is also displaceable in a piston room in the axialdirection of the directional control valve, i.e., in the same directionas the pilot piston of the hydraulic unit, and is non-positively and/orpositively connected to the pilot piston. The actuating piston dividesthe piston room into two piston room chambers, which are sealed off fromone another, so that a higher or lower pressure can be set in the firstpiston room chamber than in the second piston room chamber. The firstpiston room chamber is hydraulically connected to the actuating pistonconnection a, for example, via holes, in particular holes in the axialdirection in a housing or cylinder, in which the actuating piston issupported so it is displaceable. The second piston room chamber can becontinuously hydraulically connected to the actuating unit tankconnection t, for example, but could also be air filled and/or connectedto the surroundings of the directional control valve. Other connectionsare possible.

The actuating piston is further connected via a first elastic element,in particular a compression spring, referred to in the present case as ameasuring spring, which acts against the hydraulic pressure force in thefirst piston room chamber, to the control piston, in particularpositively and/or non-positively, or at least supported thereon, andconnected via a second elastic element, which also acts against thehydraulic pressure force in the first piston room chamber, for example,also in the form of a compression spring—referred to in the present caseas a restoring spring—to the control housing or the flange, againadvantageously positively and/or non-positively, or is at leastsupported on one of the two. The measuring spring can thus cause theabove-described retraction of the magnet armature at comparatively lowvoltages and/or current strengths of the electromagnet.

The first elastic element, in particular the measuring spring,advantageously has a different spring force than the second elasticelement, in particular the restoring spring. The first elasticelement—measuring spring—will typically have a lesser spring force thanthe second elastic element—restoring spring.

If compression springs are provided as the elastic elements, they aretypically situated in the second piston room chamber. Of course, it isalso possible to provide one or more tension springs instead ofcompression springs, in particular instead of the restoring spring,which is/are then advantageously situated in the first piston roomchamber or outside the piston room chamber.

The measuring spring is advantageously implemented having a smallerexternal diameter than the restoring spring and can thus be positionedradially inside the restoring spring in a space-saving manner. Therestoring spring encloses the measuring spring in the peripheraldirection. Both springs may have approximately the same axial lengthand/or essentially the same turn count.

An actuator according to the invention, which comprises a workingcylinder, in particular in the form of an actuating cylinder of aturbo-machine, also has a directional control valve of the describedtype, which is connected via hydraulic lines to the working cylinder forcontrolling or regulating the position of the retractable and extendablepiston and/or the piston rod of the working cylinder. As known, aposition measuring device can be connected to the working cylinder,which detects the position and/or the covered distance of the pistonand/or the piston rod of the working cylinder and is connected to acontrol unit, in particular integrated in the force-regulated magnet, inorder to regulate the actuation of the control piston and thus theactuating piston and pilot piston via the magnet as a function of themeasurement results. The directional control valve itself can be free ofany measuring device, which measures the movement or the position of oneof the pistons or components connected thereto.

The invention is to be described for exemplary purposes hereafter on thebasis of an exemplary embodiment. In the figures:

FIG. 1 shows a possible embodiment of a directional control valveimplemented according to the invention;

FIG. 2 shows a detail of the additional control unit, which is shownenlarged from FIG. 1.

The hydraulic unit may be seen in FIG. 1, which is formed by the controlhousing 2 having the pilot piston 3, which is displaceable therein inthe axial direction. The control housing 2 has four hydraulicconnections, namely a pressure connection P, a first consumer connectionA, a second consumer connection B, and a tank connection T. Theconnections are connected as described at the beginning to a hydraulicpressure supply, the two cylinder chambers of the working cylinder, anda hydraulic tank.

The pilot piston 3 has a comparatively large diameter, and thecomparatively large cross-section of the various hydraulic connectionsA, B, P, T, of which the pressure connection P and the two consumerconnections A, B are connected to annular chambers in the controlhousing 2, allow large volume flows through the directional controlvalve. The listed three annular chambers, which are formed and/ordelimited by the control housing 2 together with the pilot piston 3, maybe the only annular chambers of the hydraulic unit and/or the controlhousing 2. The pilot piston 3 has holes or slots running in the radialdirection, which allow an outflow of hydraulic medium from the firstconsumer connection A and/or the second consumer connection B to thetank connection T as a function of the axial position of the piston 3 inthe control housing 2, in that they have flow-conducting connectionsthereto, the tank connection T being implemented on a frontal end of thedirectional control valve in the axial direction thereof in theembodiment shown.

The radial holes or radial slots in the pilot piston 3 thus allow theconduction of hydraulic medium into the interior of the pilot piston 3and from there to the tank connection T.

The directional control valve is driven by a separate actuating unit 1,which comprises a 3/3 way valve having single-acting actuating piston1.5, which is situated axially thereto, having spring return. The 3/3way valve is formed by a control piston 1.1, which is situated so it isdisplaceable—also in the axial direction of the directional controlvalve here—within a flange 1.2 and implements an actuating unit pressureconnection p, an actuating piston connection a, and an actuating unittank connection t with the flange 1.2, see FIG. 2 in particular. Theactuating unit pressure connection p is connected to a separate pressuresupply and is thus protected from pressure drops due to large volumeflows in the hydraulic unit.

The control piston 1.1, which is directly connected to the magnetarmature of the force-regulated magnet 1.9, is received in a centralcylindrical hole of the flange 1.2. Two annular notches are incorporatedin the hole, which form a first chamber together with the control piston1.1, which is hydraulically connected to the actuating unit pressureconnection p and in which the hydraulic pressure of the pressureconnection thus prevails, and form a second chamber, which is connectedto conduct hydraulic medium to the actuating piston connection a.

The flow connection between the annular chamber connected to theactuating piston connection a and the actuating unit tank connection tis produced via radial holes in the control piston 1.1. From there, thehydraulic medium flows further into an installation room of twocompression springs—measuring spring 1.4 and restoring spring 1.6—whichapply pressure to an actuating piston 1.5, which is described in greaterdetail hereafter, and finally back in the flange 1.2 to the actuatingunit tank connection t. The actuating unit pressure connection p can beconnected in the same axial plane of the flange 1.2.

A cylinder 1.7 is inserted in the flange 1.2—and also in the controlhousing 2 in the present case—in which the actuating piston 1.5 issituated so it is displaceable in the axial direction of the directionalcontrol valve and is friction-sealed in relation to the inner surface ofthe cylinder 1.7, for example, via a seal or a guiding band. Theactuating piston 1.5 divides a piston room 1.10, which is delimited bythe cylinder 1.7 in the peripheral direction and at one axial end and isdelimited at the opposing axial end by the flange 1.2, into a firstpiston room chamber 1.11 and a second piston room chamber 1.12. Thefirst piston room chamber 1.11 is connected to conduct hydraulic mediumvia holes 1.13, which are introduced in the axial direction into thewall of the cylinder 1.7, to the actuating piston connection a. Thesecond piston room chamber 1.12 forms the installation room, which isconnected to the actuating unit tank connection t, for the measuringspring 1.4 and the restoring spring 1.6.

The restoring spring 1.6 is clamped between the flange 1.2 and theactuating piston 1.5. The measuring spring 1.4 has a smaller diameterthan the restoring spring 1.6 and can therefore be situated in aspace-saving manner in the interior of the restoring spring 1.6. Itsfirst axial end is supported via the rod 1.3 on the control piston 1.1and its other, opposing end is also supported on the actuating piston1.5. The measuring spring 1.4 pushes the control piston 1.1 in thedirection of the magnet 1.9 against a locking ring in the idle positionand thus always holds the composite of measuring spring 1.4, rod 1.3,and control piston 1.1 centrally and in a defined manner on the stop.

The coupling of the actuating unit 1 and/or the actuating piston 1.5 tothe pilot piston 3 of the “large directional control valve” (thehydraulic unit) is performed non-positively and positively. The narrowend of the actuating piston 1.5 is fitted in a pilot piston floor, inthe form of a disk 4 here, and is screwed thereon using multiple hexnuts. Of course, other connections also come into consideration. Forthis purpose, the narrow end of the actuating piston 1.5, which can alsobe referred to as a piston rod, extends through the cylinder cover 1.8,which is screwed frontally onto the cylinder 1.7 in the embodiment shownand forms the described axial delimitation of the piston chamber 1.10and/or the first piston room chamber 1.11. This piston rod is alsoguided through the cylinder cover 1.8 and is sealed with respectthereto, for example, using an inserted sealing ring.

For example, the magnet 1.9 is screwed frontally on to the flange 1.2,as shown, and the tappet rod of its armature presses into the center ofthe control piston 1.1 and moves the control piston 1.1 in the directionof the actuating piston 1.5 and/or the pilot piston 3. Theforce-regulated magnet 1.9 advantageously comprises the controlelectronics for the pilot drive (actuating unit 1) and for a workingcylinder (not shown) attached to the directional control valve, and isparticularly interconnected with a position measuring device of theworking cylinder, as described at the beginning. The control electronicscan be implemented as analog or digital and can be adapted with respectto the controlled system to the size of the working cylinder to becontrolled.

In the embodiment shown, the control piston 1.1, the actuating piston1.5, and the pilot piston 3 are thus situated concentrically one behindanother and aligned with one another in the axial direction. The flange1.2, the cylinder 1.7, and the control housing 2 are also situatedconcentrically to the common longitudinal axis of the various pistons.

The control method executed according to the invention using thedirectional control valve shown will be described hereafter.

After predefining a position target value for the working cylinder (notshown) using a current, in particular between 4 and 20 milliamps,applied to the magnet 1.9, which is implemented as an electromagnet, thecontroller immediately experiences a control deviation. The controlelectronics calculate a magnetic force target value therefrom as themanipulated variable. The changing magnetic force has the result thatthe magnet armature is deflected and the control piston 1.1 presses tothe right against the measuring spring 1.4. The 3/3 way valve opens,which is formed by the control piston 1.1 together with the flange 1.2,and releases the passage of the room connected to the actuating unitpressure connection p and the room connected to the actuating pistonconnection a. Armature and control piston 1.1 move in the direction ofthe actuating piston 1.5 and/or pilot piston 3 until the magnetic forceand the measuring spring force are in equilibrium. A spring balance isthus formed. The actuating piston 1.5 moves because of thepressurization of the first piston room chamber 1.11 with the supplypressure via the connection of the two cited chamber (p to a) in thedirection of the control piston 1.1 or away from the pilot piston 3 (thepositive connection between these two pistons is still to be noted) andcompresses the measuring spring 1.4 further, until it closes the passageor flow cross-section between the two chambers again, which areconnected using the actuating unit pressure connection p and/or theactuating piston connection a, using its force and holds the system inequilibrium. This equilibrium state can also be referred to as thehydraulic center.

Because of the rigid attachment of the actuating piston 1.5 on the pilotpiston 3, it also executes the movement of the actuating piston 1.5 andaccordingly regulates the flow cross-section between the hydraulicconnections A, B, P, and T of the control housing 2 of the hydraulicunit.

Vice versa, if a movement of the working cylinder piston (not shown)and, for this purpose, the pilot piston 3 is required in the otherdirection, the magnetic force is reduced, the control piston 1.1 movesin the direction away from the actuating piston 5 and/or the pilotpiston 3, and toward the magnet 1.9, and releases the passage (flowcross-section) between the chamber connected to the actuating pistonconnection a and the actuating unit tank connection t. The hydraulicmedium, in particular oil, is pressed out of the cylinder 1.7, namelythe first piston room chamber 1.11, by expansion of the restoring spring1.6. The actuating piston 1.5 moves in the direction away from thecontrol piston 1.1 (to the right in the illustration shown) and relaxesthe measuring spring 1.4. It relaxes precisely until the prevailingmagnetic force presses the control piston 1.1 to the right and ends theoutflow of the hydraulic medium from the first piston room chamber 1.11via the actuating piston connection a and the actuating unit tankconnection t to the hydraulic tank (not shown). The magnetic force andthe measuring spring force are again in equilibrium.

The magnetic force change and the stroke change of the actuating piston1.5 and thus of the pilot piston 3 are proportional to one another. Amagnetic force change is therefore always associated with a uniqueposition of the actuating piston 1.5 and thus the pilot piston 3.

An electrical conductor can be situated in the magnetic field of theforce-regulated magnet 1.9 to measure the magnetic flux density via aHall voltage induced in the conductor. This conductor (not shown) can beconnected to the magnet 1.9 and/or the control electronics for themagnet 1.9 in such a manner that the magnetic force is regulated via areturn of the Hall voltage. Therefore, the actuating piston 1.5 and thepilot piston 3 fixedly connected thereto may be positioned exactly onlyby changing the magnetic force.

The control movement of the pilot piston 3 required for the positioningof the piston rod of a large working cylinder can be performed ideallyusing the directional control valve implemented according to theinvention. A position measurement of the actuating piston 1.5 and/or thepilot piston 3 is not necessary. A position measuring system in or onthe directional control valve, which is sensitive to heat andsusceptible to failure, can therefore be dispensed with. A positionmeasuring system is advantageously only provided on the workingcylinder.

1. A directional control valve for controlling working cylinders orservomotors, in particular an actuating cylinder of a turbo-machine suchas gas and steam turbines; 1.1 having a force-regulated magnet (1.9) and1.2 having a hydraulic unit, comprising a control housing (2), in whicha pilot piston (3) is situated so it is displaceable in the axialdirection of the directional control valve, 1.3 the control housing (2)having at least three hydraulic connections, namely a first pressureconnection (P) for the connection to a hydraulic pressure supply, aconsumer connection (A, B) for the connection to the working cylinder orservomotor, and a tank connection (T) for the connection to a hydraulictank; and 1.4 the flow cross-section between the hydraulic connections(A, B, P, T) being variable by displacement of the pilot piston (3);characterized in that 1.5 an additional actuating unit (1) is provided,which comprises the force-regulated magnet (1.9) and an additionalcontrol piston (1.1), which is displaceable in the control housing (2)or in a flange (1.2) attached on the control housing (2), and which isdisplaceable using a force-regulated magnet (1.9) and which varies theflow cross-section between an actuating unit pressure connection (p), anactuating piston connection (a), and an actuating unit tank connection(t) by displacement; 1.6 the actuating unit (1) also comprising anactuating piston (1.5), which is also non-positively and/or positivelyconnected on the pilot piston (3) so it is displaceable in the axialdirection of the directional control valve, and divides a piston room(1.10) into two piston room chambers (1.11, 1.12) which are sealed toone another, of which the first chamber (1.11) is hydraulicallyconnected to the actuating piston connection (a), and 1.7 the actuatingpiston (1.5) being connected via a first elastic element, which actsagainst the hydraulic pressure force in the first piston room chamber(1.11), to the control piston (1.1) or being supported thereon, andbeing connected via a second elastic element, which acts against thehydraulic pressure force in the first piston room chamber (1.11), to thecontrol housing (2) or the flange (1.2) or being supported thereon. 2.The directional control valve according to claim 1, characterized inthat the first elastic element is implemented as a pressure element, inparticular as a compression spring (measuring spring 1.4), which ispositioned in the second piston room chamber (1.12), and/or the secondelastic element is implemented as a pressure element, in particular as acompression spring (restoring spring 1.6), which is positioned in thesecond piston room chamber (1.12).
 3. The directional control valveaccording to claim 2, characterized in that the first elastic element,in particular the measuring spring (1.4), has a different, in particularlesser spring force than the second elastic element, in particular therestoring spring (1.6).
 4. The directional control valve according toone of claim 2 or 3, characterized in that the measuring spring (1.4)has a smaller diameter than the restoring spring (1.6) and is enclosedin the peripheral direction on its outer side by the restoring spring(1.6).
 5. The directional control valve according to one of claims 1through 4, characterized in that the control piston (1.1) is alsodisplaceable in the axial direction of the directional control valve,and the pilot piston (3), the control piston (1.1), and the actuatingpiston (1.5) are situated concentrically one behind another and alignedwith one another in particular in the axial direction.
 6. Thedirectional control valve according to one of claims 1 through 5,characterized in that the directional control valve is free of aposition measuring device, which measures the position of one of thepistons (3, 1.1, 1.5) or of components connected thereto.
 7. Thedirectional control valve according to one of claims 1 through 6,characterized in that the control piston (1.1) is situated so it canslide in a cylindrical hole of the flange (1.2).
 8. The directionalcontrol valve according to one of claims 1 through 7, characterized inthat the actuating piston (1.5) is situated so it can slide inside acylinder (1.7), which is inserted into the control housing (2) and/or inthe flange (1.2) or is implemented in one piece therewith, and whichdelimits the two piston room chambers (1.11, 1.12) in the peripheraldirection and/or on one side or both sides in the axial direction, andin particular the hydraulic connection between the actuating pistonconnection (a) and the first piston room chamber (1.11) is implementedin the cylinder (1.7) in the form of one or more holes (1.13).
 9. Thedirectional control valve according to one of claims 1 through 8,characterized in that the actuating unit pressure connection (p) issealed hydraulically and pressure-tight with respect to the pressureconnection (P).
 10. The directional control valve according to one ofclaims 1 through 9, characterized in that a conductor is situated in themagnetic field of the force-regulated magnet (1.9), which is implementedas an electromagnet for an electrical activation, which is connected tothe magnet (1.9) in such a matter that the magnetic force and thus theposition of the control piston (1.1), the actuating piston (1.5), andthe pilot piston (3) are regulated via the Hall voltage generated in theconductor.
 11. An actuator, comprising a working cylinder, in particularthe form of an actuating cylinder of a turbo-machine, and a directionalcontrol valve, which is connected to the working cylinder via hydrauliclines for controlling or regulating the position of an extendable andretractable piston of the working cylinder, characterized in that thedirectional control valve is implemented according to one of claims 1through
 10. 12. The actuator according to claim 11, characterized inthat a position measuring device is connected to the working cylinder,which acquires the position and/or the covered distance of the piston ofthe working cylinder, and a control unit is provided, which regulatesthe force-regulated magnet (1.9) as a function of the measurementresults, in particular in the form of an electrical voltage, of theposition measuring device.